Fluid distribution systems are frequently installed to deliver a fluid, such as water, to one or more spraying units. Conventional uses for such spraying units include area irrigation, fire extinguishing and cooling by spray evaporation. In addition, conventional distribution systems which provide water to the spray units may be permanently buried or elevated above ground level.
Spraying units are usually required to evenly distribute the water over a selected area. The spray distribution is normally affected by the spray head or nozzle. Stationary spray heads may be used to produce a continuous spray configured to cover an area. Rotating spray heads may be used to produce a radial spray which is rotated through an arc effective to cover an area. In both cases, however, radial distribution is continuous and uniform distribution is difficult to achieve.
In order to improve spray distribution uniformity along a radial direction, systems have been developed to sweep the spray along a radial direction. For example, U.S. Pat. Nos. 1,796,940 and 1,796,941, both to Pottenger, disclose spring actuated control systems cooperating with distribution system pressure to obtain internal valve movements affecting water pressure forcing the spray units to obtain a sweeping action. These units appear to be mechanically complex with many internal parts exposed to the sprayed fluid and entrained debris.
In another example, U.S. Pat. No. 3,747,858, to Krynicki, discloses a spray head with an internal impeller which is driven by the flowing fluid. The rotating impeller produces a variable orifice and, hence, a variable output pressure forming each spray droplet. The resulting radial sweep may be very rapid and appear to be a uniformly dispersed and continuous spray. The spray head appears to require close tolerances between adjacent parts and to be possibly susceptible to damage from debris passing through the spray head and the rapidly rotating impeller.
Underground fluid distribution systems may be used where the area to be watered permits installation of underground pipes. Back-fit installation or repair of such systems is not always possible because of intervening concrete structure and plant growth. Elevated distribution systems are not suited to cover large yard areas, but are indeed suitable for small yard areas, now increasingly found in town homes, patio homes and affordable single family detached dwellings. Certainly, elevated distribution systems are required for roof-top distribution of water for evaporative cooling or fire extinguishing. Although not impossible, it is difficult to incorporate conventional spray nozzles in an elevated system to obtain the desired uniformity of spray distribution.
The disadvantages of the prior art are overcome by the present invention and improved methods and apparatus are provided to control fluid pressure in a fluid spray system to sweep the spray in a radial direction and to uniformly deliver the spray over a selected area, preferrably through an elevated distribution system.